The External Network Core is intended to use a modest level of resources to build a meaningful, integrated and lasting research and training program with researchers at the University of North Carolina, Chapel Hill (UNC-CH). Duke and UNC-CH are 10 miles apart. Both have long and strong histories in the Population Sciences. Much of Duke's strength in the Population Sciences has centered on Aging research while Population Sciences research at UNO's Carolina Population Center (CPC) has focused on issues in Child Health and Human Development and Public Health. In fact, CPC is currently the largest population center and arguably among the strongest centers funded by NICHD. The division between Aging research and research on earlier parts of the life course is becoming less well defined. All three signature themes of this application are centered on this fact. Even though CPC is an NICHD funded center, two of its eight signature themes. Biological and Social Interactions and Life Course Perspectives, overlap almost identically with two of the three themes of this proposal. Currently 13 UNC CPC members have are affiliate with CPHA. Three of these UNC researchers, Harris, Pearce and Yang, are involved in the Add Health Parent Study (Add Health-PS). This ENC is born out of what we view as a unique opportunity to extend and enhance the strong research collaboration between CPHA and UNC-CH beyond the Add Health-PS.